This study is designed to quantify and characterize Clinical Center healthcare workers' self-reported occupational parenteral and nonparenteral exposures to blood and other body substances. Participants are asked to estimate monthly parenteral and nonparenteral exposures to blood and the other body substances. These data will be used in four ways: 1) to establish current levels of exposures in the Clinical Center; 2) to compare these levels of exposure with similar data obtained in two previous surveys; 3) to establish a baseline to compare results from a subsequent survey conducted after staff have been trained according to the new standard published by the Occupational Safety and Health Administration (OSHA); and 4) to attempt to estimate underreporting of parenteral exposures by comparing participants' self-reported parenteral exposure estimates with the number of parenteral exposures reported to our Occupational Medical Service for the same time periods. During July, over 2500 questionnaires were mailed out to selected populations of healthcare workers in the Clinical Center. The questionnaire requests information on demographics, hepatitis B vaccination status, Universal Precautions training, and the occurrence of parenteral, mucous membrane, and cutaneous exposures to blood and other body substances.